Biomedical subjects

K M Mackay

Publications and source records attributed to K M Mackay.

3 recordsLinked to original sources

PubMed2001

Effect of melting point of chiral terpenes on human stratum corneum uptake.

The effect of melting point of chiral penetration enhancers on their stratum corneum uptake was investigated. The pure enantiomers of a chiral compound often possess different melting points, and therefore dissimilar solubilities, to the racemate because of variations in their crystal structure. Two terpenes, menthol and neomenthol, saturated in propylene glycol/water, were applied to stratum corneum. Racemic menthol melts at approximately 33 degrees C, some 9 degrees C lower than the pure enantiomers, whereas racemic neomenthol melts at 26 degrees C higher than the study temperature, considered as the theoretical melting point of its enantiomers, which are both liquids. Terpene solubility increased with the propylene glycol content of the vehicle. The lower melting forms of both penetration enhancers possessed the highest solubility in every vehicle. Maximum stratum corneum uptake was obtained from formulations containing the lower melting forms of each enhancer in 60% w/w propylene glycol systems (highest concentration used). Compared with menthol, the larger melting point difference between optical forms of neomenthol produced bigger differences in their uptake. Thus melting point depression of menthol and neomenthol, by selection of the appropriate optical form, increased the amount of terpene delivered to the stratum corneum, in agreement with theoretical predictions.

Calorimetry, Differential Scanning↗

PubMed1998

Advance directives: barriers to completion.

The concept of advance directives, although sound in theory, appears to be failing to meet the needs of many patients. Advance directives have been endorsed by both the healthcare profession and the general public, yet few individuals have documented their wishes for treatment preferences in end-of-life decisions. A review of 15 research articles revealed three main barriers to the completion and effective use of advance directives. These barriers are: (a) lack of education or knowledge regarding advance directives, (b) difficulties with paperwork completion, and (c) discordance between patient, family members or proxy, and provider. Future research is suggested to generate information that will facilitate meeting the needs of patients and their families in this most difficult aspect of healthcare delivery.

Advance Directives↗

PubMed1996

Excipient interaction with cetylpyridinium chloride activity in tablet based lozenges.

PURPOSE: The purpose of the investigation was to determine the effect of tablet excipients on the activity of cetylpyridinium chloride (CPC) and the relative interaction between excipients and CPC. METHODS: An analytical assay was developed to evaluate the interaction between CPC and the excipients. In vivo activity was investigated using six volunteers by determining the reduction in colony forming units recoverable from the oropharynx after sucking each proprietary lozenge separately on different days. In vitro determinations investigated the relative antimicrobial activity of aqueous solutions of the lozenges and, the effect of pH and tablet base excipients on that activity against Staphylococcus aureus, Streptococcus pyogenes and Candida albicans. RESULTS: Both in vivo and in vitro results showed that the tablet based lozenges had markedly reduced antimicrobial activities compared with previous results with a candy based lozenge (in vivo and in vitro) or the same concentration of aqueous CPC (in vitro). Magnesium stearate suspensions in CPC 250 micrograms/ml indicated that magnesium stearate adsorbed CPC and at 0.4% lozenge weight and above significantly reduced the antimicrobial activity of CPC 250 micrograms/ml. CONCLUSIONS: The reduced activity of CPC in tablet based lozenges resulted from a decreased availability of CPC in solution due to an adsorption of CPC on magnesium stearate. To avoid this reduction in activity tablet based lozenges containing CPC 250 micrograms/ml, or similar concentrations, plus magnesium stearate should contain not more than 0.3% w/w lozenge weight of the lubricant.

Administration, Oral↗